Number of strict compositions of n that are neither increasing nor decreasing.

Terms

a(0) =0a(1) =0a(2) =0a(3) =0a(4) =0a(5) =0a(6) =4a(7) =4a(8) =8a(9) =12a(10) =38a(11) =42a(12) =72a(13) =98a(14) =150a(15) =298a(16) =372a(17) =542a(18) =760a(19) =1070a(20) =1428a(21) =2600a(22) =3120a(23) =4550a(24) =6050a(25) =8478a(26) =10976a(27) =15220a(28) =23872a(29) =29950